Authenticity: Van Briggle Vase

Hello everyone! I am hoping to learn more about identifying fraudulent Van Briggle pottery and wish to make this a fun learning experience for others too. I don't like just posting to solicit responses, but would rather post my inexperienced rationale for others to critique/correct me.

I love this piece, but am concerned over its authenticity. My rationale is that this appears to have both a finisher's mark and number. From what I have read, this is a red flag. What is complicating things for me, is that the coloring appears to be consistent with Van Briggle. In this case there is a darker blue applied over the lighter, which is (to my untrained eye) consistent with their technique. I do not have a type # to compare to other examples.  

Any thoughts are much appreciated!